Today's society is highly mobile. That is, individuals can move rapidly from one location to the next by utilizing automobiles, mass transit, bicycles, and the like. The advantages of communication any time and almost anywhere, advances in technology, and the affordability of wireless communication devices, such as cell phones, pagers, personal communications systems (PCS), and personal digital assistants (PDA) have resulted in a proliferation of these wireless communication devices in this mobile society.
Concurrent with the proliferation of wireless communication devices is the increased frequency of emergency calls originated from the wireless communication devices. These emergency calls are also referred to herein as 911 calls, representing the emergency services number “911” utilized in the United States. The ability to place 911 calls from wireless devices has contributed greatly to improving public safety, and is an important resource for individuals who need help desperately, but could not previously communicate that need. Unfortunately, many mobile callers dialing 911 to report an emergency do not know exactly where they are. This lack of spatial consciousness means operators at public safety answering points (PSAPs) may not be able determine a caller's location so that emergency response personnel can be quickly and accurately dispatched to the appropriate location.
In 1996, the Federal Communications Commission (FCC) issued a Report and Order requiring all wireless carriers and cell phone manufacturers to provide the capability for automatically identifying to emergency dispatchers the location from which a wireless call is being made. The FCC's wireless 911 mandate seeks to both improve the reliability of wireless 911 services and to provide enhanced features generally available for wireline calls.
Timing for implementing the 911 call requirements is divided into two phases. Phase I requires wireless carriers to deliver to the emergency dispatcher the telephone number of a wireless handset originating a 911 call, as well as the location of the cell site or base station receiving the 911 call, which provides a rough indication of the caller's location. This phase was implemented by the end of 1998. Phase II requires carriers to deliver more specific latitude and longitude location information, known as Automatic Location Identification (ALI), to the dispatcher in response to a 911 call initiated by a wireless device.
Various location determination technologies (LDT) are being developed to locate wireless communication devices in response to the FCC 911 Phase II mandate. These technologies encompass both network-based and handset-based equipment and processes. Broadly defined, a network-based technology is one in which the wireless communication network detects the signal transmitted from a wireless communication device and uses that signal to determine the current location of the wireless device. A hand-set based technology is one in which the wireless communication device detects signals transmitted from multiple base stations and/or satellites and uses those signals to determine the current location of the wireless device. In addition, hybrid techniques make use of both network-based and handset-based technologies to produce a more robust estimate of current location in a single process.
The FCC has adopted accuracy and reliability requirements for ALI as part of the Phase II mandate. The rules for network-based technologies specify accuracy and reliability requirements of one hundred meters for sixty-seven percent of emergency calls and three hundred meters for ninety-five percent of emergency calls. The rules for handset-based technologies specify accuracy and reliability requirements of fifty meters for sixty-seven percent of emergency calls and one hundred and fifty meters for ninety-five percent of emergency calls.
The deployment of an ALI system, and in particular, one used to provide 911 call Phase II compliant services, needs to be validated with a comprehensive test of all the environments that exist in thousands of service areas, each covering hundreds of square miles, to determine whether the ALI system complies with the accuracy standards set by the FCC. The FCC further recommends a biannual post-deployment validation of the accuracy of the ALI system. Unfortunately, a comprehensive validation of an ALI system using current empirical observations is both costly and time consuming, and requires a wireless carrier to hire a large staff of both highly skilled and medium to low skilled personnel. Furthermore, a comprehensive validation of an ALI system calls for a large number of repetitive tasks and significant human intervention, which increases the probability of error.